This invention generally relates to adjustable collapsible frame devices, and more specifically to adjustable catch mechanisms for locking a vertically collapsible support frame at graduated heights particularly adaptable for baby furniture.
Vertically collapsible scissors frames are advantageously employed to support objects such as tables, trays, and other articles which can benefit from the collapsible feature to facilitate reduction of space requirements for storage and transportation. In baby furniture, such as baby walkers, play seats and feeding tables, scissors frames are particularly advantageous. Baby furniture demands collapsibility for storage and transport because it must be conveniently carried and quickly deployed in various locations and at various times. Scissors frame construction allows the supported object to be moved between a fully elevated condition to a collapsed, compact position. Further, scissors frames allow adjustable height selection of the object supported by offering varying degrees of extension of the scissors frame. For devices such as baby walkers, baby tables and the like, this feature is particularly beneficial to accommodate the natural growth of a child or adaptability between multiple children of different sizes.
Generally, a scissors frame has at least two legs pivotally connected near their mid-points. An object is generally supported by both legs above the pivotal connection. Conventionally, one leg is attached to the supported object at a pivot joint and the second leg is attached at the object at a sliding pivot joint. By moving the two supporting pivot joints towards one another, the legs pivot at their mid-points and extend the scissors frame longitudinally to raise the supported object. When the supporting pivot joints of the two legs are moved away from one another in relative position, the supported object is lowered until the frame is eventually collapsed into a storage position. Selectible height adjustment can be achieved with such a construction by arresting the movement of the support portions of the legs away from each other at selected positions.
This general construction has been used for baby walkers and the like to provide adjustable height of the supported object and convenient collapsibility for storage. Various height adjustment mechanisms have been employed to secure the sliding pivot joint in a secured position and thereby lock the frame at a selected height. Locking arms, catches and other devices have been used to releasably lock the sliding leg in a selected position on the supported object. With baby walkers, however, simplicity and convenience of such an adjustable height mechanism is essential because the operator may only have one free hand to operate the adjustable height mechanism. As a result, successful adjustment mechanisms allow operation using only a single hand.
An example of a height adjustment apparatus used in a baby walker is disclosed in U.S. Pat. No. 4,576,392. The mechanism uses a ratchet-type catch assembly for attaching a slide connection between a scissors frame and an object supported by the frame.
The assembly includes a slide disposed in a guide which is mounted to the supported object. The sliding leg is retained by the slide in a pivotable relationship. Therefore, expansion and contraction of the scissors frame is achieved by sliding movement of the slide in the fixed guide. Pawl levers are pivotally mounted on both sides of the slide and connected together at one end by a tension spring. The spring biases the pawl levers to engage the sides of the slide along a series of ratchet stops formed in the slide. Engagement of the pawls with the stops on the ratchet surface of the slide releasably secures the table at selected heights. This mechanism, however, offers only a single sliding connection between the sliding leg and the supported object. This connection, existing between the slide and the guide, is prone to translational forces, torsion and twisting which can cause binding and excessive wear. The sliding relationship is further inhibited by a spring connected between the slide and the leg to provide resilient or "bounce" support of the table. Removal of the bounce feature would require substantial modification to the construction of the device as disclosed. Furthermore, the construction offers inadequate overall structural integrity.
It is therefore desirable to have an adjustable height catch mechanism for scissors frame devices which offers enhanced torsional rigidity and structural integrity in the slide mechanism, is convenient and easy to use, offers low manufacturing cost and can be used with or without a bounce feature.